International regulations govern the placement and station keeping for geosynchronous satellites. These regulations require the ground path of a geosynchronous satellite to intersect the equator only within a tolerance window, or "orbital slot", which is allocated to the satellite. Typically, each orbital slot is centered over a single longitude and is defined about the central position by .+-.0.05 degrees to .+-.0.1 degrees of longitude. Orbital slots currently are centered at every two degrees of longitude (i.e., 180 slots exist around the earth). This separation helps to ensure that signals emitted from satellites located in adjacent orbital slots will not significantly interfere with each other.
The finite availability of orbital slots encourages satellite designers to design geosynchronous satellites having the largest possible processing and/or data-carrying capacity. The capacity of a geosynchronous satellite is typically proportional to the size of the satellite and is limited by the state of current technology. Large, prior art geosynchronous satellites are expensive to build and place in orbit. Because of the expense, it is not typically feasible to frequently replace geosynchronous satellites which have too little capacity due to inadequate size and/or outdated technology.
Another major problem in space systems is that launch costs dominate the cost equation, and the launch "throw weight" limits the on-orbit capacity of single satellites. To continue to enhance the on-orbit capability of satellites, the prior-art approach has been to increase the size of the satellites and launch vehicles. The future growth in this direction seems to have topped out for financial reasons as well as the lack of a need for large satellites for government programs. In addition, there is a movement towards smaller satellites across the industry.
In some prior art systems, multiple geostationary satellites are placed within a single orbital slot in order to increase the data carrying capacity of the system within that slot. This is referred to as co-positioning or co-location. For example, multiple geostationary Astra satellites are operated within an orbital slot centered at 19.2 degrees east. U.S. Pat. No. 5,506,780 also discloses a geostationary satellite system which includes multiple, co-located satellites.
Some prior art systems have used parallel processing techniques to increase the processing power of the system. Parallel processing refers to the concurrent or simultaneous execution of two or more processes. Parallel processing may be contrasted with serial processing, which refers to consecutive or sequential execution of two or more processes. Generally speaking, a single computing processor may engage in only serial processing, but a collection of processors or computers may be arranged in a parallel processing architecture to engage in parallel processing.
Conventional parallel processing architectures and related techniques have been devised to solve immensely complex computational problems in real time. Also, prior art systems have been devised to achieve a greater computational throughput than can be achieved with a serial processing architecture. Unfortunately, existing space-based parallel processing architectures do not accommodate alteration of existing capabilities and do not allow the addition of new capabilities.
What are needed are a method and apparatus which enable the processing and/or data carrying capacity within a particular orbital slot to be increased relative to demand and in conjunction with state-of-the-art technology.
What are also needed are a method and apparatus to eliminate the need to enhance on-orbit capabilities of satellites without increasing the size of the satellites. In addition, a need exists for a method and apparatus to provide more processing power using smaller satellites.